The present invention relates in general to the supply of a service or utility, more usually electric power or pressure medium, to a mobile appliance or machine and especially to a mobile appliance in an underground mine working.
It is known to supply electric power to an appliance, such as a locomotive or a mineral winning machine, with the aid of an electric track composed of hollow conduits or duct sections containing electric live rails and to utilize a collector or pick-up which engages through slots in the conduits to contact the live rails. Such arrangements are described, for example, in German Pat. Nos. 1515340, 2522319, 2522320 and 2522321. In order to seal off the slots in the conduits or duct sections of the prior art arrangements, elastic seals are used which engage on one another and which are pressed apart locally by the passage of the collector or pick-up. In one known form of seal, hoses are expanded by gas pressure to engage on one another. It is also known from the prior art, to introduce a protective gas under pressure in the conduits or duct sections to ensure no explosive or combustible gas can enter the duct sections. Problems can occur with the seals hitherto adopted or proposed. The hose type seal is, for example, prone to leakage of its expanding gas when it has encountered a certain amount of wear. Once the hoses begin to leak the sealing of the duct section slots fails. Also, in the prior art arrangement, the duct-sections are not reliably maintained in a sealed condition in the region of the pick-up or collector and hence protective gas must be supplied to the duct sections in relatively large quantities to supplement the loss caused by the passage of the pick-up.
A general objection of the present invention is to provide an improved construction of the aforementioned kind especially regards the sealing of the duct-section access slot.